Internal Validity - The extent to which all explanations for changes in the DV between conditions have been eliminated -- other than the IV. ie(7a)

Extraneous variable - any variable other than IV that effects DV. Control Experimental Extraneous Variable ie(7a)

Control Confound Experimental Confounding Extraneous Variable - any extraneous variable that affects one condition differently than it affects other conditions. ie(7a)

Between Subjects Designs Two (or more) Groups of Participants compared to each other. Each group has a different level of the IV. Experimental (Treatment) Group Control Group ie(7a)

Major Potential Confound: Individual Differences (I. e Major Potential Confound: Individual Differences (I.e., perhaps the participants in one group are not comparable in many ways to participants in the other group). ie(7a)

Within Subjects Design One Group of participants measured under more than one condition of the IV. Experimental Condition Control Condition Potential Confounds Since subjects cannot be in more than one condition at one time, anything that is not the same at each of the times of measurement (other than the IV) is a potential confound. ie(7a)

Pre-Post Test Designs (type of WS design) Pre-test - DV measured before Treatment - serves as baseline control condition Post-test - DV measured after Treatment ie(7a)

Confounds with Pre-Post Designs Other than the treatment (IV) what could cause difference in DV between conditions (I.e., what possible confounds could there be?) Confounds with Pre-Post Designs History - any changes that occurred between Pre and Post Test other than IV. ie(7a)

Maturation - biological/psychological changes between pre-post test. ie(7a)

Instrumentation - changes in measurement device or operational definition between pre and post test. ie(7a)

Attention Deficit Disorder? Are rates of Diabetes really increasing, or are we simply diagnosing more cases??? Attention Deficit Disorder? DUIs? ie(7a)

Testing : Changes is a person’s score for the post conditions that results from having been tested in the pre-test. Sensitization Boredom Practice ie(7a)

Attrition - subjects dropping out of the study. ANYTHING that is a difference between the before and after condition other than the IV is a confound. ie(7a)

Hokey Pokey ie(7a)

Artifact - Effect caused by the procedure rather than by the IV. Statistical Regression Artifact. - problem when subjects are assigned to groups based on the pre-test scores. - group scores will be pulled towards the mean of the DV. - Pre-test high scorers will appear to do poorer. Pre-test low scorers will appear to do better. - problem with unreliable measures ie(7a)

Not a problem if the DV is very reliable. ie(7a)

Confounds (in pre and post designs) History Maturation Instrumentation Internal Validity? Confounds (in pre and post designs) History Maturation Instrumentation Testing Attrition (Mortality) Statistical Regression Artifact* ie(7a)

Controlling for these confounds. Use a pre-post control group. Treated the same as treatment Group except IV is not manipulated between tests. Control group affected by same, history, Maturation and Regression effects. Any difference between the treatment and control groups are not due to confounds. ie(7a)

Pre-test Treatment Post-test plus confounds Control Group Experimental Group Pre-test Treatment Post-test plus confounds Control Group Pre-test confounds Post-test ie(7a)

Compare Pre-test scores. Are they the same to begin with? Selection – confound due to assignment of subjects to the Control and Treatment Groups. Compare Pre-test scores. Are they the same to begin with? But could be a difference that interacts with the treatment. - use random assignment!!!! ie(7a)

subjects assigned to treatment and control group Selection Confound subjects assigned to treatment and control group biased on a criteria (bias). Selection X (interactions) Any of the five confounds effect the control group differently than the treatment group. i.e., Alcohol treatment study - compare volunteers to non-volunteers e.g., Differential History ie(7a)

Differential Attrition Selection X (interactions) Any of the five confounds effect the control group differently than the treatment group. Differential History Differential Attrition i.e., Alcohol treatment study - compare volunteers to non-volunteers ie(7a)

Differential Attrition Weight loss Study (Diet and Exercise condition) No-Treatment Control Group Type of people that drop put of the study might depend on which study they are in. ie(7a)

How can we ensure the subjects in each condition are comparable? Random Assignment Extraneous variables still effect DV, but it should not be a confound. ie(7a)

Treatment group = size of treatment effect plus confounds Pre-test Post test Treatment Control Treatment group = size of treatment effect plus confounds Control group = estimate of the size of pre-post confounds. ie(7a)

Pre-test Post test Treatment Control Is the pre-post test change significantly greater in the Treatment Condition than in the control condition? ie(7a)